Irritable bowel syndrome subtypes: constipation, diarrhea…and mixed bowel pattern: tertium datur.

The study by Su et al. published in this issue of NGM provides helpful insight into a relatively large, yet understudied, subgroup of IBS known as IBS with mixed bowel pattern (IBS-M). These investigators found among their 289 IBS subjects who underwent detailed assessment the IBS-M subtype to be particularly common. Interestingly, prior use of laxatives or antidiarrheal agents was found to potentially explain the mixed bowel pattern in approximately 30% of patients. These IBS-M patients tended to report more severe IBS symptoms. IBS-M patients had bowel symptoms more similar to IBS-D than IBS-C, particularly with regard to the rectal urgency. Hopefully many more studies will be forthcoming to further our understanding of IBS-M.